Broad bean burn?

Out on a country walk by the middle Severn with my nephew yesterday, we came across an entire field of (small) broad beans which had been 'singed' ie the pods blackened by burning but not incinerated and the beans dried and shrivelled within. First I thought it a random accident in recent hot weather but the burning seemed too regular and controlled, done mechanically. Then we found an adjacent field of beans similarly affected. Is this last ditch pest control or part of the harvesting process or what. Never seen or heard of it before. Any farmers ready to advise?

A farmer's daughter and sister here - will that do? We regularly grew Field Beans which look like broad beans on the family farm.

They are harvested when they are dried, the pods blacken naturally and begin to shrivel - yes they do look burnt, but they're not. The pods turn black as they dry.

They will soon be harvested with the combine harvester - the dried beans will go through a series of riddlers (shaking sieves) in the combine harvester to separate them from the bits of pod, stalk and leaf (haulms).

The dried Field Beans go to the millers to be ground down to a flour and added to animal feed - they are high in protein. The haulms are usually baled and they go for winter stock feed a bit like hay. My herd of dairy goats ate a lot of bean straw in the winter as they need a lot of roughage.